In recent years, reductions in thickness, in size, and in weight are demanded for electronic apparatuses such as an IC card or a mobile phone. In order to meet the demands, a thin semiconductor chip needs to be incorporated in such electronic apparatuses. Under the circumstances, although a thickness (film thickness) of a semiconductor wafer, which is a base of a semiconductor chip, is currently 125 μm to 150 μm, it is said that the thickness needs to be 25 μm to 50 μm for a next-generation chip. Therefore, in order to obtain a semiconductor wafer having such a film thickness, it is necessary to carry out a process of reducing a thickness of the semiconductor wafer.
Such a process of reducing the thickness of the semiconductor wafer is carried out as follows: First, a supporting plate for protecting the semiconductor wafer is attached to the semiconductor wafer via (i) a tape which has adhesive layers on its both sides or (ii) an adhesive agent so that the supporting plate covers a circuit formation surface of the semiconductor wafer. Next, the semiconductor wafer is turned upside down and a thickness of the semiconductor wafer is reduced by grinding a backside surface of the semiconductor wafer with the use of a grinder. Subsequently, the backside surface of the semiconductor wafer whose thickness has been thus reduced is fixed to a dicing tape which is held by a dicing frame. Further, the supporting plate covering the circuit formation surface of the semiconductor wafer in this state is removed, and then the semiconductor wafer is divided into chips with the use of a dicing device.
In a case where the process of reducing the thickness is thus carried out, the adhesive agent and the like are left on the circuit formation surface of the semiconductor wafer after the supporting plate is removed. Therefore, it is necessary to remove the attached adhesive agent and the like so that the circuit formation surface of the semiconductor wafer becomes a clean surface. That is, it is necessary to carry out a cleaning process on the surface of the semiconductor wafer (i) after the supporting plate covering the circuit formation surface of the semiconductor wafer is removed while the semiconductor wafer is being fixed to the dicing tape and (ii) before the semiconductor wafer is divided into chips with the use of the dicing device.
When the cleaning process is carried out or the supporting plate is removed before the cleaning process, the semiconductor wafer may be placed on and held by a holding pedestal or the like.
Patent Literature 1 discloses a conventional technique to hold a semiconductor wafer. FIG. 12 is a schematic view for schematically illustrating a processing device 90 for processing a wafer in Patent Literature 1. (a) of FIG. 12 is a lateral cross-sectional view of the processing device 90, (b) of FIG. 12 is a top view of the processing device 90, and (c) of FIG. 12 is a perspective view of the processing device 90.
As illustrated in (a) of FIG. 12, the processing device 90 holds a wafer 2 which is adhered to a center part of a dicing tape 3 that has a dicing frame 4 at its outer edge. Specifically, the processing device 90 holds a process target 1 by sucking the wafer 2 with a chuck table 91 and sucking the dicing frame 4 with a sucking pad 92. In this case, a guide rod 95 movably supports the sucking pad 92 in a radial direction of the chuck table 91, and therefore the processing device 90 can deal with various sizes of dicing frames.